PrEP and PEP in Bangkok: HIV Prevention Before and After Exposure

HIV prevention has changed enormously, and two tools sit at the centre of it: PrEP and PEP. In my clinic in Sukhumvit I speak with expats and travellers about these every week, from people planning ahead to those who arrive anxious after a single encounter the night before. Both groups have good options, and knowing which is which can be the difference between worry and reassurance.

This page is a plain-English guide to how PrEP and PEP work, who each one is for, and how to start either at our walk-in clinic in Bangkok. The single most important thing to understand is timing: PEP only works if it is started quickly, so if you are reading this after a recent risk, do not wait.

PrEP vs PEP: what is the difference?

The simplest way to remember it is the timing relative to exposure. PrEP, pre-exposure prophylaxis, is taken before and around the time of possible exposure to keep you protected on an ongoing basis. PEP, post-exposure prophylaxis, is an emergency course started after a possible exposure to stop an infection from taking hold.

Who needs which?

PrEP suits people with an ongoing or foreseeable risk, for example those with multiple partners, a partner whose status is unknown or positive and not virally suppressed, or anyone who simply wants dependable, planned protection. PEP is for a specific, unexpected event that has already happened, such as a condom breaking, condomless sex with someone of unknown status, or another one-off higher-risk exposure. PrEP is the seatbelt you wear routinely; PEP is the emergency brake.

PEP: the 72-hour emergency window

PEP is a course of anti-HIV medication, usually taken for 28 days, that can prevent HIV from establishing itself after a possible exposure. It is genuinely time-critical. PEP must be started as soon as possible and within 72 hours of the exposure, and the sooner it begins, the better it works. After 72 hours it is no longer effective.

How to start PEP today

If you may have been exposed in the last three days, treat it as urgent. Come to the clinic or contact us straight away. We will assess the risk, run baseline tests, and if PEP is appropriate we can start it the same day. Do not delay while you decide, because every hour counts within that window. Our dedicated guide, PEP for HIV: the 72-hour window and how to get it in Bangkok, explains the process step by step.

PrEP: daily and on-demand options

PrEP is highly effective at preventing HIV when taken as prescribed. There are two main ways to take it. Daily PrEP means one tablet every day, giving continuous protection that suits people with a regular or unpredictable pattern of risk. On-demand PrEP, sometimes called event-based dosing, involves taking tablets around a specific planned exposure and is an option for some people, though suitability depends on individual circumstances.

Eligibility and getting started

Before starting PrEP we confirm you are HIV-negative and check that your kidneys and general health are suitable. Starting PrEP always begins with a consultation and a test, never with medication alone. We will discuss which dosing approach fits your life and risk.

Ongoing monitoring

PrEP is not a one-off prescription. It involves regular follow-up, typically every few months, to repeat HIV testing, screen for other sexually transmitted infections and check kidney function. This monitoring keeps PrEP safe and effective. Our detailed guide, PrEP: daily vs on-demand dosing, and what it costs, compares the two approaches in more depth.

Cost and confidentiality

The cost of PrEP and PEP depends on the medication used, the length of the course and the tests involved, so we will give you clear pricing at your consultation before anything begins. There are no surprises, and you can ask about cost openly.

Confidentiality is central to how we work. Our service is private and non-judgemental, and many of our patients are expats and travellers who value discretion. You never need to justify wanting protection; wanting to look after your health is reason enough. If you also want broader screening, our HIV testing in Bangkok and STD testing in Bangkok pages explain what else we offer.

When to see a doctor

See a doctor urgently if you have had a possible HIV exposure within the last 72 hours, as PEP is time-critical and may still prevent infection. See a doctor to discuss PrEP if you have an ongoing risk and want dependable protection, or if you are already on PrEP and due for your routine monitoring. And if you have any symptoms of a possible acute infection, such as fever, sore throat, swollen glands or a rash after a risk, come in to be assessed and tested.